1. Field of the Invention
The present invention relates to a multi actuator, in particular, a multi actuator to endure unexpected impact.
2. Description of the Related Art
Generally, a multi actuator serves to output electrically or electronically received audio signal or a preset bell or melody as an audible sound. Alternatively, the multi actuator serves to output a vibration signal as a termination signal. Such a multi actuator has been used for mobile communication systems such as cellular phones and pagers. However, since the multi actuator is required to always carry with its user and is mainly used in a place crowded with people, its inner structure may be deformed due to external impact or failing to hold it regardless of the user""s intention.
Accordingly, demand for a multi actuator that can endure unexpected impact is on an increasing trend.
A multi actuator recently used for mobile communication means such as cellular phones includes a case having a space therein, a vibration plate for generating sound, of which outer end portion is fixed to an upper end portion of the case, a voice coil fixed to a lower end portion of the vibration plate, a magnet magnetized vertically, an upper plate attached to the magnet, for generating a magnetic field, a yoke for generating the magnetic field together with the magnet, upper and lower plate springs used as suspension springs to support the yoke and vibration mass including weight, and a vibration coil installed in an upper surface of a shield plate, for generating vibration using a magnetic flux formed in the magnetic field. If mutual locations of the above elements and their assembled state are deformed due to external impact, the multi actuator does not fail to perform its function.
In this respect, elements used for mobile communication systems such as cellular phones and pagers are subject to a drop test in various angles and directions at a certain height. Such a drop test is carried out for the multi actuator.
For the drop test, a jig is used to apply impact to the multi actuator at a certain height. The jig is repeatedly dropped several times in all sides. At this time, an opposing drop surface is formed of a steel plate that is a rigid material enough to apply impact to the product.
It is noted from the above drop test that deformation of the prior art multi actuator occurs between a case and a plate spring during lateral drop.
FIG. 2 shows a general type of a plate spring. The plate spring is fixed to a groove formed inside a case and supports a weight. The plate spring serves to determine mass of the weight and the natural frequency of the vibration of the magnetic field. Also, the plate spring acts on sound and vibration generated depending on input exciting frequency. In other words, it is necessary to maintain a constant value k of the spring and the mass m that significantly serves to determine the natural frequency of the vibration of the magnetic field, without any change.
It is, therefore, an object of the present invention to provide a multi actuator that fixes the location of vibration mass therein and prevents characteristic of a plate spring having an elastic coefficient from being varied when the mass vibrates, the elastic coefficient and the mass determining the natural frequency of the vibration of a magnetic field.
Another object of the present invention is to provide a multi actuator for use in a mobile communication system, which prevents a plate spring from being deformed to improve reliability and vibration characteristic.
To achieve the above object, there is provided a multi actuator including a case having a space and a groove therein, a vibration plate for generating sound, of which outer end portion is fixed to an upper end portion of the case, a voice coil fixed to a lower end portion of the vibration plate, a magnet magnetized vertically, an upper plate attached to the magnet, for generating a magnetic field, a yoke for generating the magnetic field together with the magnet, upper and lower plate springs for supporting the yoke and vibration mass including a weight, and a vibration coil installed in an upper surface of a shield plate, for generating vibration using a magnetic flux formed in the magnetic field.